Too few American adults have been vaccinated for shingles, the painful sibling to chicken pox, according to research that calls for efforts to increase the U.S.-recommended inoculation. Fewer than 2 of 10 Americans ages 60 and older have been vaccinated, while the rate is less than half that for those in their 50s, according to a study presented today at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy in Denver. Almost one-third of Americans will get shingles in their lifetime, with about 1 million cases in the U.S. each year, the Centers for Disease Control and Prevention said.